Preparation of diffracting crystals of PsRubisco. (a) Purification of PsRubisco. SDS–PAGE showing ammonium sulfate (AS) fractions. The 40% fraction contained the highest proportion of Rubisco and was used directly for crystallization after dialysis to remove AS. L, large subunit; S, small subunit. (b) Crystals of PsRubisco. The approximate dimensions of the PsRubisco crystals were 50 × 50 × 20 µm.